/*-
 * Copyright 2003-2005 Colin Percival
 * All rights reserved
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted providing that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY
 * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
 * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING
 * IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 * POSSIBILITY OF SUCH DAMAGE.
 */

#if 0
__FBSDID("$FreeBSD: src/usr.bin/bsdiff/bsdiff/bsdiff.c,v 1.1 2005/08/06 01:59:05 cperciva Exp $");
#endif

#include <sys/types.h>

#include <bzlib.h>
#include <err.h>
#include <fcntl.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>

#include "com_cundong_utils_DiffUtils.h"

#define MIN(x,y) (((x)<(y)) ? (x) : (y))

static void split(off_t *I, off_t *V, off_t start, off_t len, off_t h) {
	off_t i, j, k, x, tmp, jj, kk;

	if (len < 16) {
		for (k = start; k < start + len; k += j) {
			j = 1;
			x = V[I[k] + h];
			for (i = 1; k + i < start + len; i++) {
				if (V[I[k + i] + h] < x) {
					x = V[I[k + i] + h];
					j = 0;
				};
				if (V[I[k + i] + h] == x) {
					tmp = I[k + j];
					I[k + j] = I[k + i];
					I[k + i] = tmp;
					j++;
				};
			};
			for (i = 0; i < j; i++)
				V[I[k + i]] = k + j - 1;
			if (j == 1)
				I[k] = -1;
		};
		return;
	};

	x = V[I[start + len / 2] + h];
	jj = 0;
	kk = 0;
	for (i = start; i < start + len; i++) {
		if (V[I[i] + h] < x)
			jj++;
		if (V[I[i] + h] == x)
			kk++;
	};
	jj += start;
	kk += jj;

	i = start;
	j = 0;
	k = 0;
	while (i < jj) {
		if (V[I[i] + h] < x) {
			i++;
		} else if (V[I[i] + h] == x) {
			tmp = I[i];
			I[i] = I[jj + j];
			I[jj + j] = tmp;
			j++;
		} else {
			tmp = I[i];
			I[i] = I[kk + k];
			I[kk + k] = tmp;
			k++;
		};
	};

	while (jj + j < kk) {
		if (V[I[jj + j] + h] == x) {
			j++;
		} else {
			tmp = I[jj + j];
			I[jj + j] = I[kk + k];
			I[kk + k] = tmp;
			k++;
		};
	};

	if (jj > start)
		split(I, V, start, jj - start, h);

	for (i = 0; i < kk - jj; i++)
		V[I[jj + i]] = kk - 1;
	if (jj == kk - 1)
		I[jj] = -1;

	if (start + len > kk)
		split(I, V, kk, start + len - kk, h);
}

static void qsufsort(off_t *I, off_t *V, u_char *old, off_t oldsize) {
	off_t buckets[256];
	off_t i, h, len;

	for (i = 0; i < 256; i++)
		buckets[i] = 0;
	for (i = 0; i < oldsize; i++)
		buckets[old[i]]++;
	for (i = 1; i < 256; i++)
		buckets[i] += buckets[i - 1];
	for (i = 255; i > 0; i--)
		buckets[i] = buckets[i - 1];
	buckets[0] = 0;

	for (i = 0; i < oldsize; i++)
		I[++buckets[old[i]]] = i;
	I[0] = oldsize;
	for (i = 0; i < oldsize; i++)
		V[i] = buckets[old[i]];
	V[oldsize] = 0;
	for (i = 1; i < 256; i++)
		if (buckets[i] == buckets[i - 1] + 1)
			I[buckets[i]] = -1;
	I[0] = -1;

	for (h = 1; I[0] != -(oldsize + 1); h += h) {
		len = 0;
		for (i = 0; i < oldsize + 1;) {
			if (I[i] < 0) {
				len -= I[i];
				i -= I[i];
			} else {
				if (len)
					I[i - len] = -len;
				len = V[I[i]] + 1 - i;
				split(I, V, i, len, h);
				i += len;
				len = 0;
			};
		};
		if (len)
			I[i - len] = -len;
	};

	for (i = 0; i < oldsize + 1; i++)
		I[V[i]] = i;
}

static off_t matchlen(u_char *old, off_t oldsize, u_char *new, off_t newsize) {
	off_t i;

	for (i = 0; (i < oldsize) && (i < newsize); i++)
		if (old[i] != new[i])
			break;

	return i;
}

static off_t search(off_t *I, u_char *old, off_t oldsize, u_char *new,
		off_t newsize, off_t st, off_t en, off_t *pos) {
	off_t x, y;

	if (en - st < 2) {
		x = matchlen(old + I[st], oldsize - I[st], new, newsize);
		y = matchlen(old + I[en], oldsize - I[en], new, newsize);

		if (x > y) {
			*pos = I[st];
			return x;
		} else {
			*pos = I[en];
			return y;
		}
	};

	x = st + (en - st) / 2;
	if (memcmp(old + I[x], new, MIN(oldsize-I[x],newsize)) < 0) {
		return search(I, old, oldsize, new, newsize, x, en, pos);
	} else {
		return search(I, old, oldsize, new, newsize, st, x, pos);
	};
}

static void offtout(off_t x, u_char *buf) {
	off_t y;

	if (x < 0)
		y = -x;
	else
		y = x;

	buf[0] = y % 256;
	y -= buf[0];
	y = y / 256;
	buf[1] = y % 256;
	y -= buf[1];
	y = y / 256;
	buf[2] = y % 256;
	y -= buf[2];
	y = y / 256;
	buf[3] = y % 256;
	y -= buf[3];
	y = y / 256;
	buf[4] = y % 256;
	y -= buf[4];
	y = y / 256;
	buf[5] = y % 256;
	y -= buf[5];
	y = y / 256;
	buf[6] = y % 256;
	y -= buf[6];
	y = y / 256;
	buf[7] = y % 256;

	if (x < 0)
		buf[7] |= 0x80;
}

int genpatch(int argc, char *argv[]) {
	int fd;
	u_char *old, *new;
	off_t oldsize, newsize;
	off_t *I, *V;
	off_t scan, pos, len;
	off_t lastscan, lastpos, lastoffset;
	off_t oldscore, scsc;
	off_t s, Sf, lenf, Sb, lenb;
	off_t overlap, Ss, lens;
	off_t i;
	off_t dblen, eblen;
	u_char *db, *eb;
	u_char buf[8];
	u_char header[32];
	FILE * pf;
	BZFILE * pfbz2;
	int bz2err;

	if (argc != 4)
		errx(1, "usage: %s oldfile newfile patchfile\n", argv[0]);

	/* Allocate oldsize+1 bytes instead of oldsize bytes to ensure
	 that we never try to malloc(0) and get a NULL pointer */
	if (((fd = open(argv[1], O_RDONLY, 0)) < 0)
			|| ((oldsize = lseek(fd, 0, SEEK_END)) == -1)
			|| ((old = malloc(oldsize + 1)) == NULL )
			|| (lseek(fd, 0, SEEK_SET) != 0)
			|| (read(fd, old, oldsize) != oldsize) || (close(fd) == -1))err(1, "%s", argv[1]);

	if (((I = malloc((oldsize + 1) * sizeof(off_t))) == NULL )
	|| ((V = malloc((oldsize + 1) * sizeof(off_t))) == NULL))err(1, NULL);

	qsufsort(I, V, old, oldsize);

	free(V);

	/* Allocate newsize+1 bytes instead of newsize bytes to ensure
	 that we never try to malloc(0) and get a NULL pointer */
	if (((fd = open(argv[2], O_RDONLY, 0)) < 0)
			|| ((newsize = lseek(fd, 0, SEEK_END)) == -1)
			|| ((new = malloc(newsize + 1)) == NULL )
			|| (lseek(fd, 0, SEEK_SET) != 0)
			|| (read(fd, new, newsize) != newsize) || (close(fd) == -1))err(1, "%s", argv[2]);

	if (((db = malloc(newsize + 1)) == NULL )
	|| ((eb = malloc(newsize + 1)) == NULL))err(1, NULL);
	dblen = 0;
	eblen = 0;

	/* Create the patch file */
	if ((pf = fopen(argv[3], "w")) == NULL )
		err(1, "%s", argv[3]);

	/* Header is
	 0	8	 "BSDIFF40"
	 8	8	length of bzip2ed ctrl block
	 16	8	length of bzip2ed diff block
	 24	8	length of new file */
	/* File is
	 0	32	Header
	 32	??	Bzip2ed ctrl block
	 ??	??	Bzip2ed diff block
	 ??	??	Bzip2ed extra block */
	memcpy(header, "BSDIFF40", 8);
	offtout(0, header + 8);
	offtout(0, header + 16);
	offtout(newsize, header + 24);
	if (fwrite(header, 32, 1, pf) != 1)
		err(1, "fwrite(%s)", argv[3]);

	/* Compute the differences, writing ctrl as we go */
	if ((pfbz2 = BZ2_bzWriteOpen(&bz2err, pf, 9, 0, 0)) == NULL )
		errx(1, "BZ2_bzWriteOpen, bz2err = %d", bz2err);
	scan = 0;
	len = 0;
	lastscan = 0;
	lastpos = 0;
	lastoffset = 0;
	while (scan < newsize) {
		oldscore = 0;

		for (scsc = scan += len; scan < newsize; scan++) {
			len = search(I, old, oldsize, new + scan, newsize - scan, 0,
					oldsize, &pos);

			for (; scsc < scan + len; scsc++)
				if ((scsc + lastoffset < oldsize)
						&& (old[scsc + lastoffset] == new[scsc]))
					oldscore++;

			if (((len == oldscore) && (len != 0)) || (len > oldscore + 8))
				break;

			if ((scan + lastoffset < oldsize)
					&& (old[scan + lastoffset] == new[scan]))
				oldscore--;
		};

		if ((len != oldscore) || (scan == newsize)) {
			s = 0;
			Sf = 0;
			lenf = 0;
			for (i = 0; (lastscan + i < scan) && (lastpos + i < oldsize);) {
				if (old[lastpos + i] == new[lastscan + i])
					s++;
				i++;
				if (s * 2 - i > Sf * 2 - lenf) {
					Sf = s;
					lenf = i;
				};
			};

			lenb = 0;
			if (scan < newsize) {
				s = 0;
				Sb = 0;
				for (i = 1; (scan >= lastscan + i) && (pos >= i); i++) {
					if (old[pos - i] == new[scan - i])
						s++;
					if (s * 2 - i > Sb * 2 - lenb) {
						Sb = s;
						lenb = i;
					};
				};
			};

			if (lastscan + lenf > scan - lenb) {
				overlap = (lastscan + lenf) - (scan - lenb);
				s = 0;
				Ss = 0;
				lens = 0;
				for (i = 0; i < overlap; i++) {
					if (new[lastscan + lenf - overlap + i]
							== old[lastpos + lenf - overlap + i])
						s++;
					if (new[scan - lenb + i] == old[pos - lenb + i])
						s--;
					if (s > Ss) {
						Ss = s;
						lens = i + 1;
					};
				};

				lenf += lens - overlap;
				lenb -= lens;
			};

			for (i = 0; i < lenf; i++)
				db[dblen + i] = new[lastscan + i] - old[lastpos + i];
			for (i = 0; i < (scan - lenb) - (lastscan + lenf); i++)
				eb[eblen + i] = new[lastscan + lenf + i];

			dblen += lenf;
			eblen += (scan - lenb) - (lastscan + lenf);

			offtout(lenf, buf);
			BZ2_bzWrite(&bz2err, pfbz2, buf, 8);
			if (bz2err != BZ_OK)
				errx(1, "BZ2_bzWrite, bz2err = %d", bz2err);

			offtout((scan - lenb) - (lastscan + lenf), buf);
			BZ2_bzWrite(&bz2err, pfbz2, buf, 8);
			if (bz2err != BZ_OK)
				errx(1, "BZ2_bzWrite, bz2err = %d", bz2err);

			offtout((pos - lenb) - (lastpos + lenf), buf);
			BZ2_bzWrite(&bz2err, pfbz2, buf, 8);
			if (bz2err != BZ_OK)
				errx(1, "BZ2_bzWrite, bz2err = %d", bz2err);

			lastscan = scan - lenb;
			lastpos = pos - lenb;
			lastoffset = pos - scan;
		};
	};
	BZ2_bzWriteClose(&bz2err, pfbz2, 0, NULL, NULL );
	if (bz2err != BZ_OK)
		errx(1, "BZ2_bzWriteClose, bz2err = %d", bz2err);

	/* Compute size of compressed ctrl data */
	if ((len = ftello(pf)) == -1)
		err(1, "ftello");
	offtout(len - 32, header + 8);

	/* Write compressed diff data */
	if ((pfbz2 = BZ2_bzWriteOpen(&bz2err, pf, 9, 0, 0)) == NULL )
		errx(1, "BZ2_bzWriteOpen, bz2err = %d", bz2err);
	BZ2_bzWrite(&bz2err, pfbz2, db, dblen);
	if (bz2err != BZ_OK)
		errx(1, "BZ2_bzWrite, bz2err = %d", bz2err);
	BZ2_bzWriteClose(&bz2err, pfbz2, 0, NULL, NULL );
	if (bz2err != BZ_OK)
		errx(1, "BZ2_bzWriteClose, bz2err = %d", bz2err);

	/* Compute size of compressed diff data */
	if ((newsize = ftello(pf)) == -1)
		err(1, "ftello");
	offtout(newsize - len, header + 16);

	/* Write compressed extra data */
	if ((pfbz2 = BZ2_bzWriteOpen(&bz2err, pf, 9, 0, 0)) == NULL )
		errx(1, "BZ2_bzWriteOpen, bz2err = %d", bz2err);
	BZ2_bzWrite(&bz2err, pfbz2, eb, eblen);
	if (bz2err != BZ_OK)
		errx(1, "BZ2_bzWrite, bz2err = %d", bz2err);
	BZ2_bzWriteClose(&bz2err, pfbz2, 0, NULL, NULL );
	if (bz2err != BZ_OK)
		errx(1, "BZ2_bzWriteClose, bz2err = %d", bz2err);

	/* Seek to the beginning, write the header, and close the file */
	if (fseeko(pf, 0, SEEK_SET))
		err(1, "fseeko");
	if (fwrite(header, 32, 1, pf) != 1)
		err(1, "fwrite(%s)", argv[3]);
	if (fclose(pf))
		err(1, "fclose");

	/* Free the memory we used */
	free(db);
	free(eb);
	free(I);
	free(old);
	free(new);

	return 0;
}

JNIEXPORT jint JNICALL Java_com_cundong_utils_DiffUtils_genDiff(JNIEnv *env,
		jclass cls, jstring old, jstring new, jstring patch) {
	int argc = 4;
	char * argv[argc];
	argv[0] = "bsdiff";
	argv[1] = (char*) ((*env)->GetStringUTFChars(env, old, 0));
	argv[2] = (char*) ((*env)->GetStringUTFChars(env, new, 0));
	argv[3] = (char*) ((*env)->GetStringUTFChars(env, patch, 0));

	printf("old apk = %s \n", argv[1]);
	printf("new apk = %s \n", argv[2]);
	printf("patch = %s \n", argv[3]);

	int ret = genpatch(argc, argv);

	printf("genDiff result = %d ", ret);

	(*env)->ReleaseStringUTFChars(env, old, argv[1]);
	(*env)->ReleaseStringUTFChars(env, new, argv[2]);
	(*env)->ReleaseStringUTFChars(env, patch, argv[3]);

	return ret;
}
